Linq通用分页数据查询方法

在使用EF的过程有很多需要分页查询数据的地方，但是经常重复在输入分页的相关代码，这样即不便于维护，也增加了不少工作量。

对于通用查询有几个要点，一是要动态定义查询条件，还可以动态选择所需要的列。

1、数据查询方法

Code Snippet

1. publicstaticList Query(thisIQueryable query,
2.                                                                       Expression<Funcbool>> where,
3.                                                                       Expression<Func> orderby,
4.                                                                       Expression<Funcint, TResult>> selector,
5.                                                                       bool isAsc)

 

Code Snippet

1. publicstaticList<object> Query(thisIQueryable query,
2.                                                                       Expression<Funcbool>> where,
3.                                                                       Expression<Func> orderby,
4.                                                                       Func<IQueryable, List<object>> selector,
5.                                                                       bool isAsc)

Code Snippet

1. publicstaticPageInfo<object> Query(thisIQueryable query, int index, int pageSize,
2.                                                                 Expression<Funcbool>> where,
3.                                                                 Expression<Func> orderby,
4.                                                                 Func<IQueryable, List<object>> selector,
5.                                                                 bool isAsc)

3、分页查询方法

Code Snippet

1. publicstaticPageInfo<object> Query(thisIQueryable query, int index, int pageSize,
2.                                                          List<Expression<Funcbool>>> wheres,
3.                                                          Expression<Func> orderby,
4.                                                          Func<IQueryable, List<object>> selector, bool isAsc)

 

Code Snippet

1. publicstaticPageInfo Query(thisIQueryable query, int index, int pageSize,
2.                                                          List<Expression<Funcbool>>> wheres,
3.                                                          Expression<Func> orderby,
4.                                                          Func<IQueryable, List> selector, bool isAsc)

 

Code Snippet

1. publicstaticPageInfo Query(thisIQueryable query, int index, int pageSize,
2.                                                                 Expression<Funcbool>> where,
3.                                                                 Expression<Func> orderby,
4.                                                                 Func<IQueryable, List> selector,
5.                                                                 bool isAsc)

 

工具类方法：

 

Code Snippet

1. publicclassPageInfo
2.     {
3.         publicstaticvoid CheckPageIndexAndSize(refint index, refint size)
4.         {
5.             if (index < 1)
6.             {
7.                 index = 1;
8.             }
9.  
10.             if (size < 1)
11.             {
12.                 size = 20;
13.             }
14.         }
15.  
16.         publicstaticvoid CheckPageIndexAndSize(refint index, int size, int count)
17.         {
18.             if (count >= index * size)
19.             {
20.                 return;
21.             }
22.  
23.             index = count / size;
24.             if (count % size > 0)
25.             {
26.                 index++;
27.             }
28.  
29.             if (index == 0)
30.             {
31.                 index = 1;
32.             }
33.         }
34.  
35.     }
36.  
37.     publicclassPageInfo : PageInfo
38.     {
39.         internal PageInfo()
40.         {
41.             DataList = newList();
42.         }
43.         public PageInfo(int index, int pageSize, int count, List dataList)
44.         {
45.             Index = index;
46.             PageSie = pageSize;
47.             Count = count;
48.             DataList = dataList;
49.         }
50.  
51.         publicint Index { get; privateset; }
52.         publicint PageSie { get; privateset; }
53.         publicint Count { get; privateset; }
54.         publicList DataList { get; privateset; }
55.  
56.         publicPageInfo Empty
57.         {
58.             get { returnnewPageInfo(); }
59.         }
60.     }

 

实现代码：

Code Snippet

1. publicstaticclassLinqExtent
2.     {
3.         publicstaticList Query(thisIQueryable query,
4.                                                                       Expression<Funcbool>> where,
5.                                                                       Expression<Func> orderby,
6.                                                                       Expression<Funcint, TResult>> selector,
7.                                                                       bool isAsc)
8.         {
9.             if (selector == null)
10.             {
11.                 thrownewArgumentNullException("selector");
12.             }
13.  
14.             var queryable = query;
15.             if (where != null)
16.             {
17.                 queryable = queryable.Where(where);
18.             }
19.             if (orderby != null)
20.             {
21.                 queryable = isAsc ? queryable.OrderBy(orderby) : queryable.OrderByDescending(orderby);
22.             }
23.  
24.             return queryable.Select(selector).ToList();
25.         }
26.  
27.         publicstaticList<object> Query(thisIQueryable query,
28.                                                                       Expression<Funcbool>> where,
29.                                                                       Expression<Func> orderby,
30.                                                                       Func<IQueryable, List<object>> selector,
31.                                                                       bool isAsc)
32.         {
33.             if (selector == null)
34.             {
35.                 thrownewArgumentNullException("selector");
36.             }
37.  
38.             var queryable = query;
39.             if (where != null)
40.             {
41.                 queryable = queryable.Where(where);
42.             }
43.             if (orderby != null)
44.             {
45.                 queryable = isAsc ? queryable.OrderBy(orderby) : queryable.OrderByDescending(orderby);
46.             }
47.  
48.             return selector(queryable);
49.         }
50.  
51.         publicstaticPageInfo<object> Query(thisIQueryable query, int index, int pageSize,
52.                                                                 Expression<Funcbool>> where,
53.                                                                 Expression<Func> orderby,
54.                                                                 Func<IQueryable, List<object>> selector,
55.                                                                 bool isAsc)
56.         {
57.             return Query(query, index, pageSize, newList<Expression<Funcbool>>> {where}, orderby, selector,
58.                          isAsc);
59.         }
60.         publicstaticPageInfo<object> Query(thisIQueryable query, int index, int pageSize,
61.                                                          List<Expression<Funcbool>>> wheres,
62.                                                          Expression<Func> orderby,
63.                                                          Func<IQueryable, List<object>> selector, bool isAsc)
64.         {
65.             //if (selector == null)
66.             //{
67.             //    throw new ArgumentNullException("selector");
68.             //}
69.  
70.             //PageInfo.CheckPageIndexAndSize(ref index,ref pageSize);
71.             //IQueryable queryable = query;
72.             //if (wheres != null)
73.             //{
74.             //    wheres.ForEach(p=>queryable = queryable.Where(p));
75.             //}
76.  
77.             //int count = query.Count();
78.             //PageInfo.CheckPageIndexAndSize(ref index,pageSize,count);
79.             //if (count > 0)
80.             //{
81.             //    if (orderby != null)
82.             //    {
83.             //        queryable = isAsc ? queryable.OrderBy(orderby) : queryable.OrderByDescending(orderby);
84.  
85.             //    }
86.  
87.             //    return new PageInfo